Data transmission control method for GPRS

ABSTRACT

A data transmission method of a GPRS includes estimating a possibility of an impending stall state of a transmit window, transmitting a stall state alarm signal of the transmit window to a network if it is predicted that the stall state of the transmit window is approaching, and controlling data transmissions according to whether an ACK signal for the stall state alarm signal is received or not from the network. Notification of the possibility of the stall state of the transmit window is provided at least once and preferably twice to the network before stall actually occurs, thereby reducing the number of occurrences of the transmit window&#39;s stall state. As a result, waste of network resources due to re-transmission performed in the stall state is minimized.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a General Packet Radio System(GPRS) and more particularly to a data transmission method in the GPRS.

[0003] 2. Background of the Related Art

[0004] A GPRS is an overlay network system implemented on a globalsystem for mobile communications (GSM) network, which is a circuitswitching-based two-generation radio communication network standardadapted by GPRS for packet data transmissions. In order to transmitpacket-based data on the GSM network, a fresh network factor, aninterface, and a protocol are required to process packet traffic.

[0005] The GPRS is logically implemented by adding two network nodes ascore network (CN) factors of the GSM. The first node is a serving GPRSSupport Node (SGSN) and the second node is a gateway GPRS Support Node(GGSN). In addition to these nodes, a packet control unit (PCU) forprocessing a packet traffic should be installed in a base stationcontroller (BSC), and software upgrading should also be performed.

[0006] In the GPRS system constructed as described above, voice or datatraffic transmitted from a GPRS terminal is transmitted to a BTS throughan air interface and then transmitted from the BTS to the BSC in thesame manner. However, at the output side of the BSC, the traffic isdivided into voice traffic which is transmitted to a mobile switchingcenter (MSC) as standard GSM traffic and data traffic which istransmitted to the SGSN through the PCU.

[0007] The GPRS uses a physical channel called a temporary block flow(TBF) for data transmission between the terminal and a network. The TBFis set when there is an LLC PDU transmission request by an upper layerof the terminal in a packet idle mode. When the TBF is set, the terminalis switched to a packet transfer mode.

[0008] The LLC PDU transmission service is provided in an RLCacknowledged mode and an RLC unacknowledged mode, and when the LLC PDUtransmission in uplink and downlink directions is terminated, thecorresponding TBF is released. As the TBF is released in the packettransfer mode, the terminal returns to the packet idle mode.

[0009]FIG. 1 shoes a protocol layer adopted in the GPRS system. Asshown, a data link layer consists of a logical link control (LLC), radiolink control (RLC), and medium access control (MAC) sub-layers. Thesesub-layers provide a service on an upper layer protocol and receives aservice from a physical layer. The LLC sub-layer provides a logicalchannel ensuring reliability between two peer entities, while the RLCsub-layer positioned below the LLC sub-layer segments ato-be-transmitted LLC protocol data unit (PDU) to RLC/MAC block andreassembles received RLC/MAC block. The MAC sub-layer positioned belowthe RLC sub-layer allows a plurality of mobile terminals to share aphysical channel.

[0010] The RLC/MAC block is classified into an RLC data block and anRLC/MAC control block in the acknowledged mode. The RLC/MAC controlblock has priority over the RLC data block. The RLC/MAC block consistsof an MAC header and an RLC data block which includes an RLC header, anRLC data unit, and spare bits.

[0011]FIG. 2 shows a format of an uplink RNC data block containing anMAC header adopted for the GPRS system in accordance with a related art.The MAC header consists of a payload type field indicative of a type ofdata carried in the RLC/MAC block, a countdown value field indicative ofa countdown value (CV) that the terminal transmits in order for anetwork to calculate the current number of RLC data blocks remaining forthe uplink TBF, a stall indicator (SI) bit indicative of whether an RLCtransmission window of the terminal can advance, and a retry (R) bitindicative of whether the terminal has transmitted a CHANNEL REQUESTmessage or a PACKET CHANNEL REQUEST message more than once during thelatest channel access.

[0012] An uplink RLC data block includes a spare bit set to ‘0’, an PFIindicator (PI) indicative of whether there is a packet flow identifier(PFI), an optional item, a TLLI indicator (TI) bit indicative of whetherthere is a temporary flow identity (TFI) field for checking a TBF wherethe RLC data block belongs or whether there is a TLLI field, al;optional item, a BSN field indicative of a block sequence number (BSN),a length indicator (LI) for determining a boundary of LLC PDUs of theRLC data block, a more (M) bit indicative of whether there is afollowing LLC PDU in the RLC data block, and an extension (E) bitindicative of whether there is an optional octet in the RLC PDU.

[0013] In the uplink TBF operation process, the terminal transmits theRLC/MAC block through each allocated uplink data block, and the networksends a PACTKET UNLINK ACK/NAK message to the terminal as necessary. Ifa transmission status variable V(S) is equal to the sum of anacknowledge state variable V(A) and a transmit window size (WS) moduloSNS (that is, V(S)=V(A)+WS modulo SNS), the terminal judges that thetransmit window is in a stall state. Then, the terminal sets stallindicators (SI) of every transmitted uplink RLC block to ‘1’ so as toinform the network of the stall state until the transmit window gets outof the stall state.

[0014] However, in the case that the terminal informs the network of thestall state using the following data blocks after the transmit window isin stall state, the terminal keeps re-transmitting the RLC data blockswhich have not been acknowledged from the network until it receives aPACKET UPLINK ACK/NACK message from the network and gets out of thestall, and if the stall state is prolonged, radio resources are wasted.

[0015] The above references are incorporated bit reference herein whereappropriate for appropriate teachings of additional or alternativedetails, features and/or technical background.

SUMMARY OF THE INVENTION

[0016] An object of the invention is to solve at least the aboveproblems and/or disadvantages and to provide at least the advantagesdescribed hereinafter

[0017] Another object of the present invention is to provide a datatransmission control method which minimizes waste of common resourcesrelating to RLC data block re-transmission bit estimating a possibilitythat a transmit window of a terminal is in stall and informing a networkin advance before its occurrence.

[0018] To achieve at least the above objects in whole or in parts, thereis provided a data transmission method of a GPRS including: estimating apossibility that a transmit window is stalled; transmitting a stallstate alarm signal to a network if it is estimated that the transmitwindow will enter the stall state; and controlling a data transmissionaccording to whether or not an ACK signal for the stall state alarmsignal is received from the network.

[0019] The transmit window's entering into stall occurs when a sendstate variable V(S) is equal to the sum of an acknowledge state variableV(A) and a transmission window size (WS) modulo SNS (sequence numberspace).

[0020] In the step of transmitting the stall state alarm signal, a firststall state alarm signal is transmitted, it is judged whether an ACK forthe first stall state alarm signal has been received, and if the ACK forthe first stall state alarm signal is received by a predetermined timepoint, the network is informed of reception of the ACK for the firststall state alarm signal, and the transmit window is updated accordingto the received ACK signal.

[0021] If the ACK for the first stall state alarm signal is not receivedby the predetermined time point, a second stall state alarm signal istransmitted, it is judged whether an ACK for the second stall statealarm signal has been received before the transmit window is stalled,and if the ACK for the second stall state alarm signal has beenreceived, the network is informed of the reception of the ACK for thesecond stall state alarm signal, and the transmit window is updatedaccordingly to the received ACK signal.

[0022] If, however, no ACK is received for the second stall state alarmsignal, the network is informed that the transmit window is stalled anda re-transmission procedure is performed.

[0023] The first stall state alarm signal is transmitted when thereremain RLC/MAC blocks to be transmitted which are as many as double theassigned uplink time slots until the transmit window is stalled, whilethe second stall state alarm signal is transmitted when there remainRLC/MAC blocks to be transmitted which are as many as assigned uplinktime slots until the transmit window is stalled without receiving an ACKfor the first stall state alarm signal.

[0024] The stall state alarm signal of the transmit window is determineddepending on setting of an RLC Transmit Stall Alarm (RTSA) field of theRLC data block. An RTSA field of the RLC data block corresponding to thefirst stall state alarm signal is set to ‘01’, while an RTSA field ofthe RLC data block corresponding to the second stall state alarm signalis set to ‘10’.

[0025] An RTSA field of the first RLC data block transmitted afterreceiving an ACK for the first and second stall state alarm signal isset to ‘11’, and an RTSA field of the following RLC data block is set to‘00’.

[0026] Additional advantages, objects, and features of the inventionwill be set forth in part in the description which follows and in partwill become apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objects and advantages of the invention may be realizedand attained as particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The invention will be described in detail with reference to thefollowing drawings in which like reference numerals refer to likeelements wherein:

[0028]FIG. 1 is a drawing illustrating a protocol layer adopted for aGPRS system;

[0029]FIG. 2 is a drawing illustrating a format of an uplink RLC datablock containing an MAC header in accordance with the related art;

[0030]FIG. 3 is a drawing illustrating a frame structure of uplink anddownlink channels allocated to a multislot class 12 terminal;

[0031]FIG. 4 is a drawing illustrating a format of an uplink RLC datablock containing an MCA header adopted for a data transmission method inaccordance with a preferred embodiment of the present invention; and

[0032]FIG. 5 is a flow-chart of a data transmission control method in aGPRS in accordance with the present invention

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0033] A data transmission method in accordance with the presentinvention will now be described by taking an example of channelallocation in a multislot class 12 terminal supporting a multi-timeslot. A GPRS radio frame consists of 8 time slots. Each uplink anddownlink allocation available number of the class 12 terminal is 4, andthe sum of maximum uplink and downlink is 5 An uplink frame starts laterby 3 time slots than a downlink frame in consideration of a propagationdelay.

[0034]FIG. 3 shows a frame structure of uplink and downlink channelsallocated to the multislot class 12 terminal. As shown, there isallocated four uplink time slots TS0, TS1, TS2, and TS3 (block period)and one downlink time slot TS0 per frame. The terminal transmits the RLCdata block to the network through the uplink time slots TS0, TS1, TS2and TS3. After the RLC data block is transmitted as much as the transmitwindow (WS), the terminal receives a packet uplink ACK/NACK messagethrough the downlink time slot TS0.

[0035] In this process, if the transmit window (WS) is checked to be ina stall state, the terminal sets an SI bit of the uplink RLC data blockas ‘1’ and informs the network that the RLC transmit window of theterminal is in the stall state. If the transmit window is not in thestall state, the SI bit is set to ‘0’.

[0036] When the send state variable V(S) of the terminal is equal to thesum of an acknowledge state variable V(A), which indicates a BSN valueof the oldest RLC data block negatively received from the network, andthe WS modulo SNS (sequence number space) 128 (that is, if V(S)=V(A)+WSmodulo SNS), the terminal judges that the transmit window is in thestall state. V(S), which is a sequence number of the RLC data block tobe transmitted next, has a value of SNS-1 at ‘0’. When TBF starts, V(S)starts from ‘0’ and is increased by 1 together with BSN (block sequencenumber) whenever the RLC data block is transmitted.

[0037] The acknowledge state variable V(A) provides an index withrespect to an acknowledge state array V(B) modulo SNS, which is updatedby a value of a received block bitmap (RBB) of the packet uplinkACK/NACK message received from the network. The acknowledge state arrayV(B) is an array of SNS factors informing the acknowledge state of thetransmit window size (WS). The RBB is a binary value array of the WSfactors.

[0038] If the transmit window is judged to be in the stall state, theterminal transmits the oldest RLC data block having a factor with aPENDING_ACK value in the V(B) (that is, a value of a factorcorresponding to a pertinent RLC data block in the V(B) set when eachRLC data block is transmitted), and then subsequently transmits thesecond-oldest RLC data block. After every RLC data block having acorresponding factor with the PENDING_ACK value in V(B) is transmitted,the terminal repeats transmission from the oldest RLC data block in thesame manner. The procedure of transmitting the oldest RLC data blockhaving the corresponding factor with the PENDING_ACK value in V(B)continues until V(S)=V(A)+WS modulo SNS is released.

[0039] Accordingly, if the packet uplink ACK/NACK value received fromthe network is negative or if no packet uplink ACK/NACK message isreceived, the transmit window is held in the stall state so thatre-transmission of the oldest RLC data block having the correspondingfactor with the PENDING_ACK value in V(B) is repeated to waste thecommon resource.

[0040] The present invention is directed to minimizing waste of thecommon resource according to re-transmission by allowing the terminal topredict the stall state and then informing the network in advance beforethe transmit window is stalled.

[0041]FIG. 4 shows a format of an uplink RLC data block containing anMCA header adapted for a data transmission method in accordance with apreferred embodiment of the present invention. The uplink RLC data blockpreferably uses the spare bits in the uplink RLC data block of therelated art to RLC transmit stall alarm (RTSA) bits. Alternatively, thestall alarm bits may be included in other portions or fields of the RLCdata block, and/or as new bits appended to the data block.

[0042] In the data transmission method of the present invention, theterminal predicts a stall condition of the window before the transmitwindow actually stalls, informs the network accordingly using the RTSAbits of the uplink RLC data block, and requests a packet uplink ACK/NACKmessage. The terminal's packet uplink ACK/NACK message request maybeattempted before the transmit window is stalled.

[0043] More specifically, the terminal transmits the RLC/MAC block withRTSA bits set to ‘01’ to the network when there remains RLC/MAC blocksas many as double the number of allocated uplink timeslots until thetransmit window is stalled. When the packet uplink ACK/NACK message isreceived from the network in response to the first RTSA bits, theterminal transmits the RLC/MAC block with RTSA bits set to ‘11’ to thenetwork to inform that the packet uplink ACK/NACK message has beenreceived.

[0044] Meanwhile, if no packet uplink ACK/NACK message is received forthe first RTSA bits from the network, the terminal transmits the RLC/MACblock with RTSA bits set to ‘10’ to the network when there remainsRLC/MAC blocks as many as the number of allocated uplink timeslots untilthe transmit window is stalled.

[0045] If the packet uplink ACK/NACK message is received from thenetwork in response to the second RTSA bits, the terminal transmits theRLC/MAC block with RTSA bits set to ‘11’ to the network to inform of itsreception of the packet uplink ACK/NACK. If, however, no packet uplinkACK/NACK message is received for the second RTSA bits from the network,the transmit window is stalled.

[0046] Table 1 defines each value of RTSA bits. TABLE 1 RTSA bits 00None valid 01 Request Packet uplink ACK/NACK (1st) 10 Request Packetuplink ACK/NACK (2nd) 11 Received Packet uplink ACK/NACK

[0047]FIG. 5 shows steps included in a data transmission control methodin a GPRS in accordance with one embodiment of the present invention.When an uplink TBF is set in an RLC acknowledged mode, the terminaltransmits the RLC/MAC block within the transmit window through eachallocated uplink data block (step S101). While transmitting the RLC/MACblock, the terminal monitors N_(s), the number of RLC/MAC blockscorresponding to the number of allocated ULTSs, and judges whether itsatisfies the condition of 2N_(s)=N_(t) (step S102).

[0048] If the condition 2N_(s)=N_(t) is satisfied, the terminal setsRTSA bits of the transmitted RLC data block to ‘01’, requests a packetUL ACK/NACK from the network (first packet UL ACK/NACK request) (stepS103), and waits for a packet UL ACK/NACK message from the network inresponse (step S104).

[0049] When the terminal receives the packet UL ACK/NACK from thenetwork in response to the first packet UL ACK/NACK request, theterminal sets RTSA bits to ‘11’ and informs the network of the receptionof the packet UL ACK/NACK, and then, sets RTSA bits to ‘00’ for thefollowing RLC data block.

[0050] Meanwhile, if no packet UL ACK/NACK is received from the networkfor the first packet UL ACK/NACK request, the terminal judges whetherthe condition N_(s)=N_(t) (step S105) is satisfied. If this condition issatisfied, the terminal sets RTSA bits of the RLC data block to ‘10’ andrequests a packet UL ACK/NACK from the network (second packet ULACK/NACK request) (step S106) and waits for the packet UL ACK/NACKmessage from the network in response (step S107).

[0051] When the packet UL ACK/NACK message is received from the networkin response to the second packet UL ACK/NACK request, the terminal setsRTSA bits to ‘11’ and informs the network of the reception of the packetUL ACK/NACK, and then, sets RTSA bits to ‘00’ for the following RLC datablock (step S111).

[0052] If, however, no packet UL ACK/NAKC is received from the networkfor the second packet UL ACK/NACK request, the terminal judges whetherthe transmit window has reached a stall state (step S108), and if so theterminal performs the re-transmission procedure.

[0053] During the re-transmission procedure, the terminal monitorsreception of the packet UL ACK/NACK. When the terminal receives thepacket UL ACK/NACK message, it sets RTSA bits to ‘11’ and informs thenetwork of the reception of the packet UL ACK/NACK, and then, sets RTSAbits to ‘00’ for the following RLC data block (step S111).

[0054] Meanwhile, in step S102, if the condition 2N_(s)=N_(t) is notsatisfied, the terminal judges whether a count down procedure hasstarted. If the count down procedure has not yet started, the terminalkeeps transmission of the RLC/MAC within the transmit window. Then, whenthe count down procedure starts, the terminal transmits the final RLCdata block (step S113) and releases the uplink TBF.

[0055] As so far described, the data transmission method in accordancewith the present invention has the following advantages. The possibilitythat the transmit window is stalled is informed to the network twicebefore its occurrence, so that the number of occurrences of the transmitwindow's stall state can be reduce. As a result, waste of networkresources due to re-transmission performed in the stall state can beminimized.

[0056] The foregoing embodiments and advantages are merely exemplary andare not to be construed as limiting the present invention. The presentteaching can be readily applied to other types of apparatuses. Thedescription of the present invention is intended to be illustrative, andnot to limit the scope of the claims. Many alternatives, modifications,and variations will be apparent to those skilled in the art. In theclaims, means-plus-function clauses are intended to cover the structuredescribed herein as performing the recited function and not onlystructural equivalents but also equivalent structures.

What is claimed is:
 1. A data transmission method comprising: estimating a stall state entrance of a transmit window; transmitting a stall state alarm signal when the stall state entrance is estimated; and controlling a data transmission based on a feedback signal generated in response to the stall state alarm signal.
 2. The method of claim 1, wherein the stall state entrance occurs when a send state variable V(S) become equal to a sum of acknowledge state variable V(A) and window size (WS) modulo sequence number space (SNS).
 3. The method of claim 1, wherein the transmitting includes: transmitting a first stall state alarm signal; and transmitting a second stall state alarm signal.
 4. The method of claim 3, wherein the first stall state alarm signal is transmitted when a number (Nt) of RLC data blocks to be transmitted is two times of a number (Ns) of the RLC data blocks corresponding to a number of time slots allocated until the transmit window is stalled (Nt=2Ns).
 5. The method of claim 3, wherein the second stall state alarm signal is transmitted when a number of RLC Data Blocks to be transmitted is equal to a number of the RLC data blocks corresponding to a number of time slots allocated until the transmit window is stalled (Nt=Ns).
 6. The method of claim 3, wherein the first stall state alarm signal is transmitted when a number (Nt) of RLC data blocks to be transmitted is two times of a number (Ns) of the RLC data blocks corresponding to a number of time slots allocated until the transmit window is stalled (Nt=2Ns), and the second stall state alarm signal is transmitted when the number of the RLC data blocks to be transmitted is equal to the number of the RLC data blocks corresponding to the number of time slot allocated until the transmit window is stalled (Nt=Ns).
 7. The method of claim 6, wherein the stall state alarm signal is transmitted through a RLC Transmit Stall Alarm (RTSA) field of the RLC data block.
 8. The method of claim 7, wherein the RTSA field of the RLC data block is set to “01” for the first stall state alarm signal.
 9. The method of claim 7, wherein an RTSA field of the RI-C data block is set to “10” for the second stall state alarm signal.
 10. The method of claim 7, wherein an RTSA field of the RI-C data block is set to “01” for the first stall state alarm signal and “10” for the second stall state alarm signal.
 11. The method of claim 10, wherein an RTSA field of a first RLC data block transmitted after receiving an ACK for the first and second stall state alarm signal is set to ‘11’, and an RTSA field of the RLC data block following the first RLC Data Block is set to ‘00’.
 12. The method of claim 7, wherein transmitting the first stall state alarm signal includes: determining whether or not an acknowledgement signal is received in response to the first stall state alarm signal before a predetermined time; informing the network of reception of the acknowledgement signal for the first stall state alarm signal upon reception of the acknowledgement; and updating the transmit window according to the acknowledgement signal.
 13. The method of claim 7, wherein transmitting the second stall state alarm signal includes: determining whether or not an acknowledgement signal is received in response to the second stall state alarm signal before the transmit window is stalled; informing the network of reception of the acknowledgement signal for the second stall state alarm signal upon reception of the second stall state alarm signal; and updating the transmit window according to the acknowledgement signal.
 14. The method of claim 13, wherein if no acknowledgement signal is received in response to the second stall state alarm signal, the transmit window entered in a stall state.
 15. The method of claim 1, wherein the transmitting the transmitting includes: transmitting a first stall state alarm signal to a network; determining whether or not an acknowledgement is received in response to the first stall state alarm signal; informing the network of reception of the acknowledgement for the first stall state alarm signal upon reception of the acknowledgement and updating the transmit window according to the acknowledgement; transmitting a second stall state alarm signal if the acknowledgement is not received in response to the first stall state alarm signal until a predetermined time point; determining whether or not an acknowledgement is received in response to the second stall state alarm signal before the transmit window is stalled; informing the network of reception of the acknowledgement upon reception of the acknowledgement in response to the second stall state alarm signal, and updating the transmit window according to the received acknowledgement; informing the network that the transmit window is stalled if the acknowledgement in response to the second stall state alarm signal is not received; and performing a re-transmission procedure.
 16. The method of claim 15, wherein a transmission time point of the first stall state alarm signal is when a number (Nt) of RLC data blocks to be transmitted is two times of a number (Ns) of the RLC data blocks corresponding to a number of time slots allocated until the transmit window is stalled (Nt=2Ns).
 17. The method of claim 15, wherein the transmission time point of the second stall state alarm signal is when a number of RLC Data Blocks to be transmitted is equal to a number of the RLC data blocks corresponding to a number of time slotsw allocated until the transmit window is stalled (Nt=Ns).
 18. The method of claim 15, wherein the first stall state alarm signal is transmitted when a number (Nt) of RLC data blocks to be transmitted is two times of a number (Ns) of the RLC data blocks corresponding to a number of time slots allocated until the transmit window is stalled (Nt=2Ns), and the second stall state alarm signal is transmitted when the number of the RLC data blocks to be transmitted is equal to the number of the RLC data blocks corresponding to the number of time slot allocated until the transmit window is stalled (Nt=Ns).
 19. The method of claim 18, wherein the stall state alarm signal is transmitted through a RLC Transmit Stall Alarm (RTSA) field of the RLC data block.
 20. The method of claim 19, wherein the RTSA field of the RLC data block is set to “01” for the first stall state alarm signal.
 21. The method of claim 19, wherein an RTSA field of the RLC data block is set to “10” for the second stall state alarm signal.
 22. The method of claim 19, wherein an RTSA field of the RLC data block is set to “01” for the first stall state alarm signal and “10” for the second stall state alarm signal.
 23. The method of claim 22, wherein an RTSA field of a first RLC data block transmitted after receiving an ACK for the first and second stall state alarm signal is set to ‘11’, and an RTSA field of the RLC data block following the first RLC Data Block is set to ‘00’.
 24. A method for managing data communications, comprising: predicting a stall condition of a data transmission window; and notifying a network element of the predicted stall condition before the stall occurs.
 25. The method of claim 24, wherein the predicting step includes: determining a number of RLC data blocks to be transmitted; comparing the number of RLC data blocks to be transmitted to a predetermined value; and judging existence of the stall condition based on a result of the comparing step.
 26. The method of claim 25, wherein the predetermined value is a multiple of a number of allocated uplink time slots until the transmission window stalls.
 27. The method of claim 26, wherein said multiple is one.
 28. The method of claim 26, wherein said multiple is two.
 29. The method of claim 24, wherein the notifying step includes: setting information in a predetermined field of an uplink RLC data block to be transmitted to the network element.
 30. The method of claim 29, wherein the predetermined field is an RTSA field of the uplink RLC data block.
 31. The method of claim 24, further comprising: requesting a packet uplink acknowledgment/non-acknowledgment message before the transmit window stalls.
 32. The method of claim 24, wherein the notifying step includes: transmitting a first stall state alarm signal to the network element when a number of RLC data blocks to be transmitted equals a multiple of a number of allocated time slots until the transmission window stalls.
 33. The method of claim 32, wherein said multiple of the number of allocated time slots is two times the number of allocated time slots in the transmission window.
 34. The method of claim 32, wherein the notifying step further includes: transmitting a second stall state alarm signal to the network element when a number of RLC data blocks to be transmitted equals the number of allocated time slots until the transmission window stalls.
 35. A data block, comprising: RLC data; and a field containing information predicting a stall condition of a data transmission window.
 36. The data block of claim 35, wherein said field is an RTSA field of the data block.
 37. The data block of claim 36, wherein said field includes a value predicting the stall condition for a first time.
 38. The data block of claim 36, wherein said field includes a value predicting the stall condition for a second time.
 39. A signal, comprising: information predicting a stall condition of a data transmission window.
 40. The signal of claim 39, wherein said information is included in an RTSA field.
 41. The signal of claim 39, wherein said field includes a value predicting the stall condition for a first time.
 42. The signal of claim 39, wherein said field includes a value predicting the stall condition for a second time.
 43. A communications terminal, comprising: a transceiver; and an estimator which predicts a stall condition of a data transmission window.
 44. The terminal of claim 43, wherein the estimator determines a number of RLC data blocks to be transmitted, compares the number of RLC data blocks to be transmitted to a predetermined value, and judges existence of the stall condition based on a result of the comparison.
 45. The terminal of claim 44, wherein the predetermined value is a multiple of a number of allocated uplink time slots until the transmission window stalls.
 46. The terminal of claim 45, wherein said multiple is one.
 47. The terminal of claim 45, wherein said multiple is two.
 48. The terminal of claim 43, further comprising: a signal generator which generates an alarm signal indicative of the predicted stall condition.
 49. The terminal of claim 48, wherein the signal generator sets information in a predetermined field of an uplink RLC data block.
 50. The terminal of claim 49, wherein the predetermined field is an RTSA field of the uplink RLC data block.
 51. The terminal of claim 48, wherein the transceiver transmits a first stall condition alarm signal when a number of RLC data blocks to be transmitted equals a multiple of a number of allocated time slots until the transmission window stalls.
 52. The terminal of claim 51, wherein said multiple of the number of allocated time slots is two times the number of allocated time slots in the transmission window.
 53. The terminal of claim 51, wherein the transceiver transmits a second stall state alarm signal when a number of RLC data blocks to be transmitted equals the number of allocated time slots until the transmission window stalls. 